Track assembly for endless track vehicles

ABSTRACT

A track assembly for endless track vehicles is disclosed utilizing endless, elastomeric-sheathed, elastomer-impregnated glass fiber cable structures on which are strung individual track sections composed of a lug unit and a shoe plate unit. Each of the lug units includes passageways extending transversely of the length dimension thereof for receiving the continuous sheathed cable structures. The lug units are held in spaced apart relation from each other by integral, regularly spaced elastomeric projections extending laterally from the sides of the cable structures. The shoe plate units are secured to each of the lug units and hold the sheathed cable structures in position in the passageways without substantial compressive loading of the cable structures. The elastomeric sheath is bonded to the elastomer impregnated cables, substantially eliminating relative movement between the cables and the surrounding sheath. A load exerted on any individual track section by the drive sprocket of the track vehicle is shared with the adjacent track sections. Movement between the track sections is limited to that within the elastic limit and below the tear limit of the sheath and cables embedded in the sheath. Each of the lug units is provided with means forming a mechanical stop which prevents flexing of the cables beyond their elastic limit and means for engaging the drive sprocket of the vehicle through which vehicle drive forces are transmitted to the track assembly. Integral rails projecting from each of the lug units transversely of their length dimension and substantially parallel to the passageways for the cable structures extend beyond the opposite sides of the lug units and are engageable with the rails of adjacent lug units to limit lateral movement of the track sections relative to each other.

United States Patent 1 Snellman 11 3,734,577 51 May 22, 1973 [54] TRACKASSEMBLY FOR ENDLESS TRACK VEHICLES [75] Inventor: Donald L. Snellman,Seattle, Wash. [73] Assignee: Norfin, Inc., Seattle, Wash.

' 221 Filed: Nov. 16, 1970 [21] Appl. No.: 89,822

[52] US. Cl. ..305/40, 305/49, 305/43 [51] Int. Cl. ..B62d 55/24 [58]Field of Search ..305/38, 37, 40, 35 EB, 305/49, 43

[56] Reierences'Cited UNITED STATES PATENTS 2,596,919 5/1952 Smith..305/38 2,487,813 ll/1949 Knox ..305/38 3,480,339 11/1969 Kell 305/35EB 2,378,427 6/1945 Myers ..305/38 2,392,988 1/1946 Keck ..305/383,063,758 11/1962 Fikse 305/43 X 3,598,454 8/1971 Richards... .305/35 EB3,606,921 9/1971 Grawey ..152/354 Primary ExaminerRichard J. JohnsonAttorney-Seed, Berry & Dowrey [57] ABSTRACT A track assembly for endlesstrack vehicles is disclosed utilizing endless, elastomeric-sheathed,elastomer-impregnated glass fiber cable structures on which are strungindividual track sections composed of a lug unit and a shoe plate unit.Each of the lug units includes passageways extending transversely of thelength dimension thereof for receiving the continuous sheathed cablestructures. The lug units are held in spaced apart relation from eachother by integral, regularly spaced elastomeric projections extendinglaterally from the sides of the cable structures. The shoe plate unitsare secured to each of the lug units and hold the sheathed cablestructures in posi' tion in the passageways without substantialcompressive loading of the cable structures. The elastomeric sheath isbonded to the elastomer impregnated cables, substantially eliminatingrelative movement between the cables and the surrounding sheath. A loadexerted on any individual track section by the drive sprocket of thetrack vehicle is shared with the adjacent track sections. Movementbetween the track sections is limited to that within the elastic limitand below the tear limit of the sheath and cables embedded in thesheath. Each of the lug units is provided with means forming amechanical stop which prevents flexing of the cables beyond theirelastic limit and means for engaging the drive sprocket of the vehiclethrough which vehicle drive forces are transmitted to the trackassembly. Integral rails projecting from each of the lug unitstransversely of their length dimension and substantially parallel to thepassageways for the cable structures extend beyond the opposite sides ofthe lug units and are engageable with the rails of adjacent lug units tolimit lateral movement of the track sections relative to each other.

10 Claims, 9 Drawing Figures PAIimg uismzms 3,734,577

sum 1 OF 4 F 2 DONALD L N SEQ A N /wiw ATTORNEYS PAH-INTEL EH22 I975SHEET 2 BF 4 INVENTORS DONALD L. SNELLMAN BY uo(, flu); 4M

ATTORNEYS PATENTEL ,,'.Y22 i975 SHEET 3 OF 4 INVENTORS DONALD L.SNELLMAN ATTORNEYS PAIENT W22 ma SHEET a UF 4 N MA NL EE Mm w w 6 A N oW ATTORNEYS TRACK ASSEMBLY FOR ENDLESS VEHICLES This invention relatesto a track assembly for endless track vehicles and to the individualtrack sections making up the track assembly.

2., Prior Art Relating to the Disclosure Track assemblies for endlesstrack vehicles in common use today consist of a roller chain assemblyengaged by the drive sprocket wheel of the vehicle. Shoes provided withgrousers are bolted to the chain links to provide the bed for traction.Flexing of the chain around the drive sprocket wheel of the vehicle ispermitted by movement of roller pinions within collars fastened to thechain links. Each of these roller pinions and collars become individualwear points during use of the track assembly. As each of theseindividual points wear the sum total of their wear-substantiallyincreases the total track length of the track assembly to the pointwhere it is thrown from the vehicle drive and- /or idler wheels and mustbe replaced.

Attempts have been made to string track sections along endless cables toovercome the problems associated with conventional track assembliesmentioned above. Due to expense, elongation of the cables and otherproblems, track assemblies strung along endless cables have not becomecommercially feasible. Patents disclosing track assemblies utilizingendless cables includethe following: US. Pat. Nos. 1,230,504; 1,956,472;2,063,762; 2,402,042; 2,845,308 and 3,063,758.

To overcome problems of elongation of the cables used in endless trackassemblies a coreless, elastomerimpregnated glass fiber cable has beendeveloped which, when embedded in and bonded to a continuous, outerelastomeric sheath, provides the required flexibility and strengthnecessary for tying track sections together. Such cables are not subjectto substantial elongation to a degree that track performance anddurability can be extended beyond that normally possible forconventional track systems. These glass fiber cables, their method ofmanufacture and their use in the manufacture of endless track vehiclesare disclosed in copending application Ser. No. 718, filed Jan. 5, i970,in the names of Donald L. Snellman and Willard G. I-Iudson, assigned tothe assignee of this application.

SUMMARY OF THE INVENTION spaced intervals, a plurality of projectionsextending laterally from the sides thereof, these projections acting asspacers to locate and provide sockets for the individual track sectionswhich enclose the elastomeric- 'sheathed cable structures as well asprotect the metal track sections from metallic contact and wear. The lugunits of each track section are elongated members having open-endedpassageways extending therethrough for receipt of the sheathed cablestructures. The upper surfaces of the passageways are bevelled to formconvex surfaces relative to the width dimension of the track units, eachhaving a radius of curvature approximating the pitch diameter of thevehicle drive sprocket over which the track assembly is mounted. Eachlug unit is also provided with integral rails extending transversely ofthe length dimension of the lug unit and substantially parallel to thepassageways, the respective ends of the rails extending beyond theopposite sides of the lug unit and engageable with the rails of adjacentlug units to limit lateral movement of the track sections relative toeach other. The rails of adjacent lug units are adapted to interlock andthereby resist lateral movement of the track sections. The upper surfaceof each of the rails is flat and dimensioned to the recesses of therollers, carriers, and idler wheels of the vehicle on which the trackassembly is mounted. The rails on adjacent lug units may be providedwith respective proje'cting studs and complimentary recesses whereby tointerlink the lug units together and provide a positive mechanical stopmeans for resisting loading of the track system tending to flex thetrack and associated cable structures in reverse.

The objects of this invention are:

. to provide a track system for endless track vehicles employing endlesselastomeric-sheathed cable structures along which are strung individualtrack sections composed of a lug unit and, a grousered shoe unit;

. to provide a track system for endless track vehicles which can beutilized by existing vehicles without modification;

3. to provide a track system for endless track vehicles wherein the lugunit and grousered shoe unit of each individual track section areenclosed about the continuous sheathed cable structures withoutsubstantial compressive loading of the cable structures;

4. to provide a track system for track vehicles wherein the grousers ofthe grousered shoe units are offset from the central axis thereof sothat, when they are secured to the respective lug units, the moment ofrotation caused by the offset mounting aids in preventing the sheathedcable structures from slipping relative to the track section;

5. to provide a track system for endless track vehicles wherein theindividual track sections enclosed around the sheathed cable structuresare maintained a predetermined distance from each other by integralelastomeric projections extending laterally from the sides of thesheathed cable structures;

. to provide a track system for endless track vehicles wherein all ofthe lug and grousered shoe units making up each of the track sectionsare, respectively, of the same size and shape and wherein the lug unitscan be forged and the grousered shoe units can be rolled;

7. to provide a track system for endless track vehicles which, costwise, is competitive with existing track systems and whose performanceand durability is much improved over conventional track systems;

8. to provide a track system wherein mechanical stop means integral witheach of the lugs and/or grousered shoe units interact with adjacent lugand/or grousered shoe units to prevent flexing of the cables embedded inand bonded to the continuous elastomeric sheath beyond their elasticlimits.

9. to provide a track system for endless track vehicles which isrelatively noisefree in operation due to the elastomeric spacers betweenthe individual track sections; and

10. to provide a track system wherein loading of an individual tracksection by the drive sprocket of the vehicle about which the track istrained is shared by adjacent track sections with relative movementbetween the track sections and the elastic sheath limited to that withinthe elastic limit and short of the tear limit of the sheath and withsubstantially no relative movement between the elastomeric sheath andthe embedded cables.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of avehicle employing the track assembly of this invention;

FIG. 2 is a cross sectional view of a track section and cable structuresalong section line 2-2 of FIG. 1;

FIG. 3 is a perspective view of a portion of the traclt assemblyincluding the sheathed cable structures, lug units and grousered shoeplates;

FIG. 4 is a perspective view of a portion of a modfied track assemblydesign employing similar concepts to the track assembly of FIG. 3;

FIG.' 5 is a cross sectional view of a single track section of the trackassembly of FIG. 4',

FIG. 6 is a side view illustrating the functioning of the v mechanicalstop means as the track assembly is flexed in one direction about thedrive or carrier wheels of the DESCRIPTION OF THE PREFERRED EMBODIMENTFIG. 1 shows a conventional tractor 1 having an under carriage frame 2.At the back end of the frame a drive sprocket wheel 3 is mounted forrotation and at the forward end of the frame a carrier wheel 4 ismounted for rotation. Between the drive sprocket wheel 3 and the carrierwheel 4 are a plurality of track rollers 5 mounted for-rotation relativeto the undercarriage frame 2. Idler rollers 6 are also provided. Aroundthe ,drive sprocket'wheel, carrier wheel, track rollers and idlerrollers is trained an endless track 10 movable over-the plurality oftrack rollers, idler rollers, and carrier wheel. The endless track isdriven by the sprocket wheel 3 which transmits power from the powermeans of the tractor to the track. The track assembly 10 includes aplurality of individual track sections strung along endless, flexiblecable structures. The cable structures consist of one or more cableshaving high tensile'strength and low elongation properties embedded inand bonded to an elastomeric sheath. Preferred areelastomer-impregnatedglass fiber cables made as disclosedin application Ser. No. 718, filedJan. 5,

v 1970, entitled Glass Fiber Cable, Method of Making,

and Its Use in the Manufacture of Track Vehicles acteristicssignificantly better than steel cable. To pro-.

long the effective life of glass fiber cables the individual glassfibers making up the cables must be kept free of abrasive rubbingagainst each other and not subjected to extreme flexing as this causesfracture of the individual filaments making up the cables. Referring toFIG. 3 and FIG. 9 coreless, elastomer-impregnated glass fiber cables 11,made in accordance with the disclosure of application Ser. No. 718 aresheathed and bonded to a continuous elastomeric cushion 12. Theelastomeric cushion (1) protects the cables from contortion under loadand enables the cables to resist damage from excess'wear, shock loadingand shear,- (2) protects the cables from direct contact with theindividual track sections, and (3) prevents contact of the cables withforeign materials such as rock, sand or other abrasive materials, Theelastomer cushion, as shown, is substantially rectangular in shape;however, differently designed cushions may be employed depending on thedesign of the track sections.

The elastomeric cushion is provided with integral, elastomericprojections 13 extending laterally from each of the vertical sides ofthe cushion 12 at regularly spaced intervals. These projections serve asspacers to locate and provide sockets for the lug units which enclosethe elastomeric cable structures. The elastomeric projections also serveto separate the individual lug units of the individual track sections toprevent metal to metal contact and wear. Separation between the tracksections also results in quiet operation of the track assembly incontrast to the noisy operation of conventional track assemblies. Theprojections are shaped so that angular displacement of the individualtrack sections enclosed around the cable structures, as they travelaround the drive sprocket 3 or the carrier wheel 4, compresses theprojections and transmits horizontal compressive forces to the embeddedglass fiber cables resisting their radial distortion as they flex intothe radius of the drive sprocket or carrier wheel.

A lug unit 14 and grousered shoe plate 15 enclose the sheathed cablesbetween each of the projections 13. The lug unit and grousered shoeplate are bolted or otherwise secured together by suitable means 16. Thelug units which encase the elastomeric cable structures provide a meansof attachment for the grousered shoe plates, provides means throughwhich the drive sprocket 3 is able to drive the track assembly, andprovides a base for the attachment of integral rails upon which thetrack rollers and idler rolls ride to support the vehicle on its trackbed. Two different designs of lug units are illustrated by FIGS. 2 and3, and FIG-S. 4 to 9 respectively. The lug unit of FIGS. 4 to 9 can beforged as a single piece whereas each lug unit of FIG. 2 and 3 includesthree separate pieces. Each of the lug units is provided with parallel,open-ended passageways 17 and 18 extending transversely of the lengthdimension of the unit. The passageways are shaped to correspond with theouter contour of the elastomeric cable structures. The passageways aresized such that when the lug units are encased around the elastomericcable structures and the grousered shoe plates secured thereto, thecables embedded in the elastomeric sheath 12 are not subjected tosubstantial compressive forces. The inner side surfaces 19a of thepassageways are made to bow outwardly as shown in FIG. 7 a smallamount-not enough to pinch or compress the cable structuressubstantially. The double curvature of the side walls aids in preventingslippage of the cable structures in that extrusion'of the sheath 12 ofthe cable structures would have to result before slippage could 'occur.The width of each of the lug units is approxi mately the distancebetween the projections 13 extending laterally from each side of theelastomeric cushion 12. The upper surfaces 19 of each of the passagewaysare contoured relative to the width of the lug units toa radius ofcurvature substantially equal to the radius of an arc segment of thedrive sprocket and carrier wheel about which the track assembly is to betrained. The contoured surfaces provide a bed for the cable structureswhich is circumferential as the track assembly flexes around the drivesprocket 3 and the carrier wheel 4 and eliminated angular flexion of thecable structures which would occur if the surfaces were flat, thusavoiding undue flexing of the cables and minimizing the possibility offracture of individual filaments making up the cables.

The respective ends 18 and 19 (see FIG. 3) of each of the lug units maybe bevelled as shown to allow space for the bases of the lug sections tomove closer together as they flex about drive sprocket 3 and carrierwheel 4. Spacing of the lug units is controlled by the projections 13integral with the elastomeric cable structures.

As differentiated from the lug unit design of FIGS. 4 to 9, the lugunits of FIGS. 2 and 3 include semicircular studs 20 extending from'theinner side surfaces of the units. These semi-circular studs fit into theopen ends of a semi-circular hollow sprocket piece 21. The legs of thesprocket pieces 21 are welded to the grousered shoe plates 15 as shownin FIGS. 2 and 3. The sprocket pieces are adapted to fit in the'valleysbetween the sprockets of the drive sprocket 3.

The lug unit of FIGS. 4 to 9 is a one-piece member wherein the sprocketpiece 21 is integral with the remainder of the unit. The lug unit isbolted to the grousered shoe plate at three or more points as shown inFIG. 9 or secured thereto by other suitable means.

Integral with each of the lug units are rails 22 projecting upwardlyfrom each side of the body of the lug unit and extending transversely ofthe body and substantially parallel to the passageways 17 and 18. Theends of the rails extend beyond the opposite ends of the lug unitIAsshown the forward end of the rail on each lug unit is laterally offsetfrom the opposite end of the rail so that the rails on adjacent lugunits can be interlocked to resist lateral forces tending to laterallydisplace a track section from its adjacent section. The top surfaces ofthe rails 22 are flat. The width of the interlocking rails isdimensioned to fit in the recesses of the track rollers 5, idler rollers6 and carrier wheel 4.

The rails on each of the lug units may be provided with a stud andrecess to interlink adjacent lug units. As shown in FIGS. 2 and 3 oneend of the rail of a lug unit may be provided with a recess 23 in theside surface thereof and the other end of the rail provided with aprojecting stud 23. on the opposite side surface. This interlinkingfeature provides a positive means of resisting the effects of reverseflexing and loading of the track assembly when projecting objects areencountered in the path of travel of the vehicle. The projecting studson the rails of each unit are sized to interlink and interlock with therecesses of adjacent rails of an adjacent lug unit. By reverse flexingis meant flexing of the track assembly opposite its direction of flexingas the track travels around the drive sprocket and carrier wheel of thevehicle. Reverse flexing causes high vertical shear loads to be exertedon the cable structures at points between adjacent track sections.Reverse track flexing is resisted when the reverse bend radius lengthensthe distance between adjacent track sections to a point where contact ofthe rail stud is made with the mating wall of the recess. This contactresists further kinking of the adjacent track sections and reversebending of the cable structures and thereby prevents damaging verticalshear effects to the cable structures. In addition the interlinkingrails provide a secondary linkage to hold the track sections togethereven if the primary linking system, the endless cable structures, failsbecause of accidental causes or from wear. This secondary linkage canmaintain the integrity of the track sections to prevent jumping of thetrack from the vehicle undercarriage and allow the vehicle to beoperated until such time as the track can be repaired or replaced. Thissecondary track linkage is not to be considered a permanent linkage butwill enable the vehicle to perform limited temporary service such ascompleting a shift operation or traveling to a place of repair where thetrack assembly can be replaced or repaired.

The grousered shoe plates 15 which are secured to the underside ofeachof the lug units generally extend lengthwise beyond the ends of thelug units. The forward side of each shoe plate includes an integralprojecting shoulder 24 extending the length of the plate. The rearwardside of each plate also includes a projecting shoulder 24 which extendsbeneath and overlaps with the forward projecting shoulder 24 of anadjacent plate, providing a mechanical stop which prevents reverseflexing of the cable structures beyond a predetermined amount as shownin FIG. 6.

Each of the lug units and each of the grousered shoe plates making upthe track assembly of FIG. 4 to 9 are identical. The lug units can befabricated by forging methods and the grousered shoe plates fabricatedby rolling. Likewise the respective lug units and grousered shoe platesmaking up the track assembly of FIGS. 2 and 3 are identical. Referringto FIG. 9 the track assembly is put together by securing the cablestructures in the passageways of each of the lug units at spacedintervals between the spaced projections 13 on the cable structures.Grousered shoe plates 15 are then secured to the lower surfaces of thelug units and bolted or otherwise secured. It is preferred that littlecompressive force be exerted on the cable structures by the lug unitsduring bolting of the lug units to thegrousere'cl shoe plates. Byminimizing the compressive forces exerted on the cable structures damageto the glass fiber cables by fracture is minimized.

In the event that certain track section become damaged and need repairthe individual track sections can be replaced by a new unit withoutundue time or expense. Each of the track sections can be separated fromthe remainder of the sections and unbolted and removed with ease.

Referring to FIGS. and 6, it is preferred that the grouser on each ofthe shoe plates be offset from a center line extending the lengthdimension thereof. This serves at least two purposes. As the track movesfrom ground contact upward about carrier wheel 4 the separating movementof the grousers effected by their tilting releases dirt packed betweenthem to effect automatic cleaning. Further the offset mounting of thegrousers causes each of the track sections to have a moment of rotationabout their centers of gravity causing the lug units to bite into theelastomeric sheath of the cable structures a predetermined amount. Thebite of the lug units against the elastomeric sheath of the cablestructures caused by the offset mounting of the grouser plates aids inpreventing slippage of the cable structures through the individual tracksections.

In US. Pat. No. 3,063,758 (FIG. 31) individual track I block with theresult that a compressive load is exerted on the cable behind the drivesprocket of the vehicle with slack occurring in the track behind thedrive sprocket.

passed around the drive sprocket and is between the drive sprocket andthe carrier wheel.

In the track assembly of this invention the cable or cables are bondedto the elastomeric sheath. There is thus little or no relative movementbetween'the sheath and cable. Movement is limited to the distancebetween the individual track sections and this is calculated to bewithin the elasticlimit and short of the tear limit of the elastomericsheath. The load transmitted to the cable by the drive-sprocket throughthe lug unit of the track section and the elastomeric sheath is reactedback along the cables not as a compressive load as is true with thedesign described in US. Pat. No. 3,063,758 but as a tension load. Thecable or cables are thus pulled about the drive sprocket andnotpushed,'thus obviating the problem of slack in the track assembly.

The elastomeric-sheathed cable structures have a predetermined tearstrength. As described each of the lug units is provided with mechanicalstop means which interact with adjacent units to prevent the cablestructures from being flexed beyond their limit. Thus, before theultimate tear strength of the cables is reached the mechanical stopmeans on the lug units interact pre venting the cables from beingdamaged.

The embodiments of the invention in which a particular property orprivilege is claimed are defined as follows:

1.- An endless track assembly for a track vehicle comprising:

primary linking means for the track assembly extending circumferentiallythereof including one or more endless, flexible cables of lineardimensional stability under normal loading conditions and of hightensile strength embedded within and bonded to a continuous, unbroken,elastomeric sheath having By the term cable behind the drive sprocket ismeant that portion of the cable which has 8 integral elastomericprojections extending laterally therefrom on both sides at regularlyspaced intervals,

a plurality of track sections, each including (1) a lug unit havingmeans to grip the elastomeric sheath of the linking means yet notsubject the imbedded cables of the linking means to substantialcompressive loading, and (2) shoe plates secured together around thelinking means, the track sections disposed in side-by-side relationshipbetween the laterally extending projections on the linking means, theintegral elastomeric projections of the linking means separating thetrack sections from one another and, as the track assembly travelsaround a drive sprocket of the track vehicle, the track sectionscompressing the projections and transmitting horizontal compressiveforces to the imbedded cables of the linking means, resisting theirradial distortion, and means on each of the track sections interactingwith adjacent track sections preventing flexing of the imbedded cablesbeyond their elastic limit opposite their directions of flexing as thetrack assembly travels around the drive sprocket and carrier wheel ofthe vehicle.

2. The track assembly of claim. 1 wherein the cables are made up ofelastomer-impregnated glass fibers.

3. The track assembly of claim 1 wherein each shoe plate includes anintegral grouser on the underside thereof extending transversely of thedirectionof travel of the track assembly and offset from a mid-lineextending the length dimension of the shoe plate sufficiently to providea moment of rotation about the center of gravity of each track sectionon contact of the grouser thereof with a work surface to cause the lugunit and shoe plate to grip the linking means and prevent slippingthereof through the lug unit and shoe plate.

4. An endless track assembly for a track vehicle comprising: Y

a pair of primary linking means disposed side-by-side in parallelplanes, each linking means including one or. more endless, flexible,elastomer-impregnated glass fiber cables embedded within and bonded to acontinuous, unbroken, elastomeric sheath having integralelastomericprojections extending laterally therefrom on both sides at regularlyspaced intervals, Y a plurality of track sections strung in side-by-siderelationship on the linking means, each track section composed of a lugunit of greater length than width secured around the linking meansbetween the laterally extending projections thereof, and extendingtransversely to the length dimension of the linking 7 means, and agrousered shoe plate secured to the lug unit without substantialcompressive loading of the embedded cables therein, each lug unitincluding (1) parallel passageways for receiving the linking meanstherein with the upper surfaces thereof beveled to form convex surfaces,each having a radius of curvature approximating the radius of curvatureof an arc segment of a vehicle drive sprocket about which the trackassembly is to be trained, thereby avoiding flexing damage to theembedded cables as they travel around the drive sprocket, (2) integralrails projecting upwardly and transversely thereof substantiallyparallel to the passageways having their respective ends extendingbeyond the opposite sides of the lug unit and coacting with the rails ofan adjacent lug unit to limit relative lateral movement of. the tracksections (3) mechanical stop means of adjacent lug units to preventflexing of the embedded cables beyond their elastic limit and (4) meanson the lug unit for engaging a vehicle drive sprocket through which thetrack vehicle drive forces are transmitted to the track assembly.

5. The track assembly of claim 4 wherein the top surfaces of the railsare flat and of a width to fit the recesses of a carrier wheel, trackroller and idler wheel of a conventional endless track vehicle.

6. The track assembly of claim 5 wherein one end of the rail is providedwith a laterally extending stud and the other end of the rail isprovided with a complementary recess, the stud and recess of each lugunit adapted to coact with studs and recesses of adjacent lug units toprovide a positive mechanical stop means resisting loading of theembedded cables'tending to flex the embedded cables beyond their elasticlimit.

7. A track section of an endless series of units forming a continuoustrack assembly strung along primary linking means composed of one ormore endless, flexible elastomer-impregnated glass fiber cables embeddedsurfaces each having a radius of curvature approximating the radius ofcurvature of an arc segment of a vehicle drive sprocket about which thetrack assembly is to be trained,

integral rails projecting upwardly from the lug unit substantiallyparallel to the passageways, the respective ends of the rails extendingbeyond the opposite sides of the lug unit and adapted to overlap orcoact with the rails of an adjacent lug unit to hold the lug unitrigidly interconnected in a comto substantial compressive forces.

9. The track section of claim 7 wherein the grouser of each shoe plateextends transversely of the direction of travel of the track assemblyand is offset from the "mid-line of the plate relative to the lengthdimension thereof sufficiently to provide a moment of rotation about thecenter of gravity of the track section on contact of the grouser with awork surface to cause the lug unit and shoe plate to grip the linkingmeans and prevent slippage thereof.

10. An endless track assembly for a track vehicle comprising:

one or more endless flexible cables of linear dimensional stabilityunder normal loading conditions and of high tensile strength embeddedwithin and bonded to a continuous, unbroken elastomeric sheath havingelastomeric projections extending laterally therefrom at regularlyspaced intervals,

plurality of track sections secured around the sheath in-side-by-siderelation between the laterally extendingprojections without substantialcompression loading of the embedded cables, the distance between thetrack sections being such that load exerted on one of the track sectionsby a'drive sprocket of a track vehicle is transmitted to the adjacenttrack sections before relative movement occurs between the track sectionand the sheath and before the tear strength of the sheath is exceeded,thereby maintaining the endless cable under tension over its length.

1. An endless track assembly for a track vehicle comprising: primarylinking means for the track assembly extending circumferentially thereofincluding one or more endless, flexible cables of linear dimensionalstability under normal loading conditions and of high tensile strengthembedded within and bonded to a continuous, unbroken, elastomeric sheathhaving integral elastomeric projections extending laterally therefrom onboth sides at regularly spaced intervals, a plurality of track sections,each including (1) a lug unit having means to grip the elastomericsheath of the linking means yet not subject the imbedded cables of thelinking means to substantial compressive loading, and (2) shoe platessecured together around the linking means, the track sections disposedin side-by-side relationship between the laterally extending projectionson the linking means, the integral elastomeric projections of thelinking means separating the track sections from one another and, as thetrack assembly travels around a drive sprocket of the track vehicle, thetrack sections compressing the projections and transmitting horizontalcompressive forces to the imbedded cables of the linking means,resisting their radial distortion, and means on each of the tracksections interacting with adjacent track sections preventing flexing ofthe imbedded cables beyond their elastic limit opposite their directionsof flexing as the track assembly travels around the drive sprocket andcarrier wheel of the vehicle.
 2. The track assembly of claim 1 whereinthe cables are made up of elastomer-impregnated glass fibers.
 3. Thetrack assembly of claim 1 wherein each shoe plate includes an integralgrouser on the underside thereof extending transversely of the directionof travel of the track assembly and offset from a mid-line extending thelength dimension of the shoe plate sufficiently to provide a moment ofrotation about the center of gravity of each track section on contact ofthe grouser thereof with a work surface to cause the lug unit and shoeplate to grip the linking means and prevent slipping thereof through thelug unit and shoe plate.
 4. An endless track assembly for a trackvehicle comprising: a pair of primary linking means disposedside-by-side in parallel planes, each linking means including one ormore endless, flexible, elastomer-impregnated glass fiber cablesembedded within and bonded to a continuous, unbroken, elastomeric sheathhaving integral elastomeric projections extending laterally therefrom onboth sides at regularly spaced intervals, a plurality of track sectionsstrung in side-by-side relationship on the linking means, each tracksection composed of a lug unit of greater length than width securedaround the linking means between the laterally extending projectionsthereof, and extending transversely to the length dimension of thelinking means, and a grousered shoe plate secured to the lug unitwithout substantial compressive loading of the embedded cables therein,each lug unit including (1) parallel passageways for receiving thelinking means therein with the upper surfaces thereof beveled to formconvex surfaces, each having a radius of curvature approximating theradius of curvature of an arc segment of a vehicle drive sprocket aboutwhich the track assembly is to be trained, thereby avoiding flexingdamage to the embedded cables as they travel around the drive sprocket,(2) integral rails projecting upwardly and transversely thereofsubstantially parallel to the passageways having their respective endsextending beyond the opposite sides of the lug unit and coacting withthe rails of an adjacent lug unit to limit relative lateral movement ofthe track sections (3) mechanical stop means of adjacent lug units toprevent flexing of the embedded cables beyond their elastic limit and(4) means on the lug unit for engaging a vehicle drive sprocket throughwhich the track vehicle drive forces are transmitted to the trackassembly.
 5. The track assembly of claim 4 wherein the top surfaces ofthe rails are flat and of a width to fit the recesses of a carrierwheel, track roller and idler wheel of a conventional endless trackvehicle.
 6. The track assembly of claim 5 wherein one end of the rail isprovided with a laterally extending stud and the other end of the railis provided with a complementary recess, the stud and recess of each lugunit adapted to coact with studs and recesses of adjacent lug units toprovide a positive mechanical stop means resisting loading of theembedded cables tending to flex the embedded cables beyond their elasticlimit.
 7. A track section of an endless series of units forming acontinuous track assembly strung along primary linking means composed ofone or more endless, flexible elastomer-impregnated glass fiber cablesembedded within and bonded to a continuous, unbroken, elastomeric sheathhaving integral elastomeric projections extending laterally therefrom onboth sides at regular spaced intervals, comprising: a lug unit ofgreater width than length having a plurality of parallel, open endedpassageways extending transversely of the length dimension thereof forreceiving the linking means therein, the top surfaces of the passagewaysbeveled to form convex surfaces each having a radius of curvatureapproximating the radius of curvature of an arc segment of a vehicledrive sprocket about which the track assembly is to be trained, integralrails projecting upwardly from the lug unit substantially parallel tothe passageways, the respective ends of the rails extending beyond theopposite sides of the lug unit and adapted to overlap or coact with therails of an adjacent lug unit to hold the lug unit rigidlyinterconnected in a Common plane against pressure exerted in a lateraldirection, and a grousered shoe plate secured to the underside of thelug unit, the shoe plate coacting with the lug unit to hold the linkingmeans in parallel passageways and provide a lower surface adapted tocontact a work surface over which the track section is run.
 8. The tracksection of claim 7 wherein each of the side surfaces of the parallelpassageways are beveled to form convex outer surfaces which grip thelinking means yet do not subject the embedded cables therein tosubstantial compressive forces.
 9. The track section of claim 7 whereinthe grouser of each shoe plate extends transversely of the direction oftravel of the track assembly and is offset from the mid-line of theplate relative to the length dimension thereof sufficiently to provide amoment of rotation about the center of gravity of the track section oncontact of the grouser with a work surface to cause the lug unit andshoe plate to grip the linking means and prevent slippage thereof. 10.An endless track assembly for a track vehicle comprising: one or moreendless flexible cables of linear dimensional stability under normalloading conditions and of high tensile strength embedded within andbonded to a continuous, unbroken elastomeric sheath having elastomericprojections extending laterally therefrom at regularly spaced intervals,a plurality of track sections secured around the sheath in-side-by-siderelation between the laterally extending projections without substantialcompression loading of the embedded cables, the distance between thetrack sections being such that load exerted on one of the track sectionsby a drive sprocket of a track vehicle is transmitted to the adjacenttrack sections before relative movement occurs between the track sectionand the sheath and before the tear strength of the sheath is exceeded,thereby maintaining the endless cable under tension over its length.